From c843dda187bd44a12d8a2b1b56aebfc7f671b820 Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Wed, 7 Oct 2026 17:55:40 +0000 Subject: [PATCH] xen/netfront: drop RX packets with a short Ethernet header handle_incoming_queue() pulls pull_to bytes into the head before calling eth_type_trans(). pull_to is the length of the first RX slot, capped at RX_COPY_THRESHOLD, and that length comes from the backend. Nothing checks it against ETH_HLEN. If the first slot is shorter than ETH_HLEN and more slots follow, the head ends up shorter than an Ethernet header while skb->len is longer, and eth_type_trans() BUG()s in __skb_pull(). If the whole packet is shorter than ETH_HLEN, eth_type_trans() reads the header past the end of the data instead. Pull at least ETH_HLEN, and drop the packet if that fails, which also drops packets too short to hold an Ethernet header. This also checks the return value of the pull, which was ignored. This is XSA-522 / CVE-2026-98375 Fixes: 0d160211965b ("xen: add virtual network device driver") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Josef Bacik Message-ID: <20261007-b4-xen-netfront-short-head-v1-1-12d7113a7e4e@toxicpanda.com> Reviewed-by: Juergen Gross Signed-off-by: Juergen Gross --- drivers/net/xen-netfront.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c index 2ed673649c48..d269457e839e 100644 --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -1234,8 +1234,16 @@ static int handle_incoming_queue(struct netfront_queue *queue, while ((skb = __skb_dequeue(rxq)) != NULL) { int pull_to = NETFRONT_SKB_CB(skb)->pull_to; - if (pull_to > skb_headlen(skb)) - __pskb_pull_tail(skb, pull_to - skb_headlen(skb)); + /* pull_to comes from the first slot's length, which the + * backend controls. Make sure the head holds at least an + * Ethernet header for eth_type_trans(). + */ + if (!pskb_may_pull(skb, max(pull_to, ETH_HLEN))) { + kfree_skb(skb); + packets_dropped++; + queue->info->netdev->stats.rx_errors++; + continue; + } /* Ethernet work: Delayed to here as it peeks the header. */ skb->protocol = eth_type_trans(skb, queue->info->netdev); -- 2.55.0